Molding system

ABSTRACT

A forming system includes a heating unit that causes a current to flow through a plated metal material to heat the metal material, a forming die that forms the heated metal material, and a plating deviation suppression mechanism that suppresses a deviation of a plating in the metal material due to energization heating.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a bypass continuation of International PCT Application No.PCT/JP2022/007696, filed on Feb. 24, 2022, which claims priority toJapanese Patent Application No. 2021-032758, filed on Mar. 2, 2021,which are incorporated by reference herein in their entirety.

BACKGROUND Technical Field

A certain embodiment of the present invention relates to a formingsystem.

Description of Related Art

In the relation art, a forming system described in the related art isknown. In this forming system, a metal material is heated and the heatedmetal pipe material is formed by a forming die, so that the metal pipematerial is shaped into a shape of a forming surface of the forming die.In addition, the metal material is quenched at the same time as theforming.

SUMMARY

According to an embodiment of the present invention, there is provided aforming system according to an aspect of the present invention includesa heating unit that causes a current to flow through a plated metalmaterial to heat the metal material, a forming die that forms the heatedmetal material, and a plating deviation suppression mechanism thatsuppresses a deviation of a plating in the metal material due toenergization heating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a forming systemaccording to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a specific exampleof the forming system shown in FIG. 1 .

FIG. 3 is a schematic configuration diagram showing a specific exampleof the forming system shown in FIG. 1 .

FIG. 4 is a schematic configuration diagram showing a specific exampleof the forming system shown in FIG. 1 .

FIGS. 5A to 5D are schematic cross-sectional views showing a state of adeviation of a plating.

FIGS. 6A to 6C are diagrams showing a distribution of a magnetic fieldgenerated around a metal material during energization heating.

FIGS. 7A to 7C are diagrams for explaining a Lorentz force generated ina plate-shaped metal material.

FIGS. 8A and 8B are conceptual diagrams for explaining a force generatedbetween a metal material and a magnetic body.

FIG. 9 is a graph of a current and a graph of a transition of atemperature.

FIGS. 10A to 10C are diagrams for explaining a Lorentz force generatedin a metal pipe material.

FIG. 11 is a conceptual diagram showing a magnetic shield.

FIGS. 12A to 12C are diagrams showing analysis results indicating arelationship between a Lorentz force and a distance between a metal pipematerial and a die.

FIG. 13 is a diagram showing experimental results.

FIGS. 14A and 14B are diagrams showing experimental results.

FIGS. 15A to 15C are diagrams showing experimental results.

FIGS. 16A and 16B are diagrams showing experimental results.

FIG. 17 is a diagram showing experimental results.

FIG. 18 is a schematic configuration diagram showing a specific exampleof the forming system shown in FIG. 1 .

FIG. 19 is a schematic configuration diagram showing a specific exampleof the forming system shown in FIG. 1 .

DETAILED DESCRIPTION

Here, in a case where forming is performed by bringing the heated metalmaterial into contact with the forming die as described above, oxidescales may be generated on a surface of the metal material due toheating. Therefore, there is a case where the generation of the oxidescales is suppressed by plating the surface of the metal material.However, there is a case where a plating is melted when energizationheating is performed, and a deviation of the plating occurs due to aninfluence of a magnetic field generated by an energization current.

An aspect of the present invention has been made in view of the abovecircumstances, and it is desirable to provide a forming system capableof reducing a deviation of a plating in a metal material.

In the forming system, the heating unit causes a current to flow throughthe plated metal material to heat the metal material. Therefore, theplating may be melted by the heat of energization heating. On the otherhand, the forming system is provided with the plating deviationsuppression mechanism that suppresses the deviation of the plating inthe metal material due to energization heating. Therefore, it ispossible to suppress the deviation of the plating which is melted due toenergization heating. As described above, it is possible to suppress thedeviation of the plating of the metal material.

The plating deviation suppression mechanism may electrically suppressthe deviation of the plating. In this case, the plating deviationsuppression mechanism can easily suppress the deviation of the platingby electrical adjustment during energization heating.

The plating deviation suppression mechanism may suppress a change in acurrent when energization heating is stopped. In this case, in a casewhere a magnetic body exists around the metal material, it is possibleto suppress a magnitude of a force generated between the metal materialand the magnetic body due to a sudden change in the current.

The plating deviation suppression mechanism may suppress a current forenergization heating. In this case, in a case where the magnetic bodyexists around the metal material, it is possible to suppress themagnitude of the force generated between the metal material and themagnetic body during energization heating.

The plating deviation suppression mechanism may mechanically suppressthe deviation of the plating. In this case, a force generated duringenergization heating in relation to the magnetic body existing aroundthe metal material can be suppressed by structural consideration.

The plating deviation suppression mechanism may separate the metalmaterial and the magnetic body from each other by a predetermineddistance or more during energization heating. In this case, it ispossible to suppress a force generated between the magnetic body and themetal material during energization heating.

The plating deviation suppression mechanism may be configured by theheating unit that heats the metal material outside the forming die. Inthis case, it is possible to suppress an influence of a force generatedbetween the forming die and the metal material during energizationheating.

The plating deviation suppression mechanism may be configured by amagnetic shield disposed around the metal material during energizationheating. In this case, it is possible to suppress the generation of theforce between the forming die and the metal material during energizationheating.

Hereinafter, a preferred embodiment of the present invention will bedescribed with reference to the drawings. In addition, in the respectivedrawings, the same portions or corresponding portions are designated bythe same reference signs, and duplicated descriptions will not berepeated.

FIG. 1 is a block diagram showing a configuration of a forming system100 according to the present embodiment. In addition, FIGS. 2 to 4 areschematic configuration diagrams showing specific examples of theforming system 100 shown in FIG. 1 .

The forming system 100 is a system for manufacturing a formed product byheating a plated metal material and forming the heated metal materialwith a forming die. As the metal material, a pipe-shaped metal pipematerial 40 as shown in FIG. 2 or a plate-shaped metal material 50 asshown in FIG. 3 is adopted. As the metal material, for example, a carbonsteel material, an MnB steel material having improved hardenability, orthe like is adopted. In the present embodiment, a plated metal materialis adopted. The plated metal material is a material in which a surfaceof a steel material is covered with a plating. Details of the platingwill be described later.

As shown in FIG. 1 , the forming system 100 includes a heating unit 101,a forming device 103 having a forming die 102, and a plating deviationsuppression mechanism 104.

The heating unit 101 causes a current to flow through the plated metalmaterial to heat the metal material. The heating unit 101 includes anelectrode for causing the current to flow through the metal material bycoming into contact with the metal material, and a power supply forcausing the current to flow through the electrode. Accordingly, due toan electric resistance of the metal material itself, the metal materialitself generates heat by Joule heat (energization heating). The formingdevice 103 is a device that forms the metal material heated by theheating unit 101 with the forming die 102.

For example, as the forming device 103, a configuration shown in FIG. 2may be adopted. The forming device 103 shown in FIG. 2 is a device thatperforms forming and quenching by supplying a fluid to the heated metalpipe material 40 and bringing the fluid into contact with a formingsurface of the forming die. The forming device 103 includes the heatingunit 101.

As shown in FIG. 2 , the forming device 103 is a device that forms ametal pipe having a hollow shape by blow forming. Here, the formingdevice 103 is installed on a horizontal plane. The forming device 103includes the forming die 102, a drive mechanism 3, a holding unit 4, theheating unit 101, a fluid supply unit 6, a cooling unit 7, and a controlunit 8. In addition, in the present specification, the metal pipematerial 40 (metal material) refers to a hollow article beforecompletion of the forming by the forming device 103. The metal pipematerial 40 is a steel-type pipe material that can be hardened.Additionally, in the horizontal direction, a direction in which themetal pipe material 40 extends during forming may be referred to as a“longitudinal direction”, and a direction perpendicular to thelongitudinal direction may be referred to as a “width direction”.

The forming die 102 is a die that forms a metal pipe from the metal pipematerial 40, and includes a lower die 11 and an upper die 12 that faceeach other in a vertical direction. The lower die 11 and the upper die12 are made of steel blocks. Each of the lower die 11 and the upper die12 is provided with a recessed portion in which the metal pipe material40 is accommodated. With the lower die 11 and the upper die 12 in closecontact with each other (die closed state), respective recessed portionsthereof form a space having a target shape in which the metal pipematerial is to be formed. Therefore, a surface of each of the recessedportions serves as the forming surface of the forming die 102. The lowerdie 11 is fixed to a base stage 13 via a die holder or the like. Theupper die 12 is fixed to a slide of the drive mechanism 3 via a dieholder or the like.

The drive mechanism 3 is a mechanism that moves at least one of thelower die 11 and the upper die 12. In FIG. 2 , the drive mechanism 3 hasa configuration in which only the upper die 12 is moved. The drivemechanism 3 includes a slide 21 that moves the upper die 12 such thatthe lower die 11 and the upper die 12 are joined together, and apull-back cylinder 22 serving as an actuator that generates a force forpulling the slide 21 upward, a main cylinder 23 serving as a drivesource that downward-pressurizes the slide 21, and a drive source 24that applies a driving force to the main cylinder 23.

The holding unit 4 is a mechanism that holds the metal pipe material 40disposed between the lower die 11 and the upper die 12. The holding unit4 includes a lower electrode 26 and an upper electrode 27 that hold themetal pipe material 40 on one end side in the longitudinal direction ofthe forming die 102, and a lower electrode 26 and an upper electrode 27that holds the metal pipe material 40 on the other end side in thelongitudinal direction of the forming die 102. The lower electrodes 26and the upper electrodes 27 on both sides in the longitudinal directionhold the metal pipe material 40 by sandwiching vicinities of the endportions of the metal pipe material 40 from the vertical direction. Inaddition, groove portions having a shape corresponding to an outerperipheral surface of the metal pipe material 40 are formed on an uppersurface of the lower electrode 26 and a lower surface of the upperelectrode 27. The lower electrode 26 and the upper electrode 27 areprovided with drive mechanisms (not shown) and are movable independentlyin the vertical direction.

The heating unit 101 heats the metal pipe material 40. The heating unit101 is a mechanism that heats the metal pipe material 40 by energizingthe metal pipe material 40. The heating unit 101 heats the metal pipematerial 40 in a state in which the metal pipe material 40 is spacedapart from the lower die 11 and the upper die 12 between the lower die11 and the upper die 12. The heating unit 101 includes the lowerelectrodes 26 and the upper electrodes 27 on both sides in thelongitudinal direction as described above, and a power supply 28 thatcauses a current to flow through the metal pipe material 40 via theelectrodes 26 and 27.

Here, a state in which the metal pipe material 40 is disposed inside theforming die 102 is a state in which the metal pipe material 40 isdisposed in a space between the upper die 12 and the lower die 11 withrespect to the upper die 12 and the lower die 11 facing each other. Inthis state, the metal pipe material 40 faces the upper die 12 in a stateof being spaced downward with respect to the upper die 12, and faces thelower die 11 in a state of being spaced upward with respect to the lowerdie 11.

The fluid supply unit 6 is a mechanism that supplies a high-pressurefluid into the metal pipe material 40 held between the lower die 11 andthe upper die 12. The fluid supply unit 6 supplies a high-pressure fluidto the metal pipe material 40 which has become a high-temperature stateby being heated by the heating unit 101 and expands the metal pipematerial 40. The fluid supply units 6 are provided on both end sides ofthe forming die 102 in the longitudinal direction. The fluid supply unit6 includes a nozzle 31 that supplies a fluid from an opening portion ofan end portion of the metal pipe material 40 to the inside of the metalpipe material 40, a drive mechanism 32 that moves the nozzle 31 forwardand backward with respect to the opening portion of the metal pipematerial 40, and a supply source 33 that supplies the high-pressurefluid into the metal pipe material 40 via the nozzle 31. The drivemechanism 32 causes the nozzle 31 to be brought into close contact withthe end portion of the metal pipe material 40 in a state in whichsealing performance is secured during fluid supply and exhaust, andcauses the nozzle 31 to be spaced apart from the end portion of themetal pipe material 40 at other times. In addition, the fluid supplyunit 6 may supply a gas such as high-pressure air or inert gas as thefluid. Additionally, the fluid supply unit 6 may include the heatingunit 101 together with the holding unit 4 having a mechanism that movesthe metal pipe material 40 in the vertical direction as the same device.

The cooling unit 7 is a mechanism that cools the forming die 102. Bycooling the forming die 102, the cooling unit 7 can rapidly cool themetal pipe material 40 when the expanded metal pipe material 40 has comeinto contact with the forming surface of the forming die 102. Thecooling unit 7 includes a flow path 36 formed inside the lower die 11and the upper die 12, and a water circulation mechanism 37 that suppliescooling water to the flow path 36 and circulates the cooling water.

The control unit 8 is a device that controls the entire forming device103. The control unit 8 controls the drive mechanism 3, the holding unit4, the heating unit 101, the fluid supply unit 6, and the cooling unit7. The control unit 8 repeatedly performs an operation of forming themetal pipe material 40 with the forming die 102.

The control unit 8 controls the drive mechanism 3 to lower the upper die12 and bring the upper die 12 close to the lower die 11 to close theforming die 102. On the other hand, the control unit 8 controls thefluid supply unit 6 to seal the opening portions of both ends of themetal pipe material 40 with the nozzle 31 and supply the fluid.Accordingly, the metal pipe material 40 softened by heating expands andcomes into contact with the forming surface of the forming die 102.Then, the metal pipe material 40 is formed so as to follow a shape ofthe forming surface of the forming die 102. In addition, in a case wherea metal pipe with a flange is formed, a part of the metal pipe material40 is made to enter a gap between the lower die 11 and the upper die 12,and then the die is further closed to crush the entering portion to forma flange portion. When the metal pipe material 40 comes into contactwith the forming surface, quenching of the metal pipe material 40 isperformed by being rapidly cooled with the forming die 102 cooled by thecooling unit 7.

In addition, as the forming device 103, a configuration shown in FIG. 3may be adopted. The forming device 103 shown in FIG. 3 is a device thatperforms forming and quenching by bringing the heated flat plate-shapedmetal material 50 into contact with the forming surface of the formingdie 102. The forming device 103 includes the heating unit 101.

The forming device 103 includes the forming die 102 that forms a formedproduct by forming the metal material 50. The forming die 102 includesan upper die 62 that comes into contact with an upper surface of themetal material 50 and a lower die 63 that comes into contact with alower surface of the metal material 50. The forming surface (lowersurface) of the upper die 62 and the forming surface (upper surface) ofthe lower die 63 may be formed in a shape corresponding to, for example,a hat shape or the like. The forming device 103 includes a drive unit(not shown) that moves at least one of the upper die 62 and the lowerdie 63. The forming device 103 forms the metal material 50 into theshape of the formed product by sandwiching the metal material 50 betweenthe forming surface of the upper die 62 and the forming surface of thelower die 63. In addition, the configuration of the forming die 102 isnot limited to a configuration in which dies are disposed so as to faceeach other in the vertical direction as the upper die 62 and the lowerdie 63, and the dies may be disposed so as to face each other in ahorizontal direction. In addition, the number of dies constituting theforming die 102 is not limited to two, and the dies may be divided intothree or more.

The heating unit 101 heats the metal material 50 disposed inside theforming die 102. Here, a state in which the metal material 50 isdisposed inside the forming die 102 has the same meaning as in FIG. 2 ,and is a state in which the metal material 50 is disposed in a spacebetween the upper die 62 and the lower die 63 with respect to the upperdie 62 and the lower die 63 facing each other.

The heating unit 101 causes a current to flow through the metal material50 to heat the metal material 50. Specifically, the heating unit 101includes a pair of electrodes 70A and 70B and a power supply 71. Theelectrodes 70A and 70B are members that come into contact with the metalmaterial 50 and cause a current to flow through the metal material 50.Accordingly, due to an electric resistance of the metal material 50itself, the metal material 50 itself generates heat by Joule heat(energization heating). The power supply 71 is connected to theelectrodes 70A and 70B and causes a current to flow through the metalmaterial 50 via the electrodes 70A and 70B.

In the example shown in FIG. 3 , the electrodes 70A and 70B are incontact with the end portions of the metal material 50 in thelongitudinal direction, respectively. The arrangement in which theelectrodes 70A and 70B are in contact with the metal material 50 is notparticularly limited. In addition, although the electrodes 70A and 70Bmay have a function of holding the metal material 50, a holdingmechanism other than the electrodes 70A and 70B may be separatelyprovided. In addition, the configuration in which the electrodes 70A and70B are provided with respect to the forming device 103 is notparticularly limited. For example, the electrodes 70A and 70B may beattached to the forming die 102. In this case, the electrodes 70A and70B may be removed from the forming die 102 at a timing when theenergization heating is completed and the upper die 62 and the lower die63 are closed. Alternatively, the electrodes 70A and 70B may be providedat positions separated from the forming die 102 so that the upper die 62and the lower die 63 do not interfere with the electrodes 70A and 70Beven when the upper die 62 and the lower die 63 are closed. Further, theelectrodes 70A and 70B may be provided with an actuator (not shown) suchthat the electrodes 70A and 70B are movable with respect to the formingdie 102.

As shown in FIG. 3 , the forming system 100 includes a control unit 80.The control unit 80 is a device that controls the entire forming system100. The control unit 80 is electrically connected to the power supply71 of the heating unit 101. The control unit 80 controls a heatingtiming by the heating unit 101 by transmitting a control signal to thepower supply 71 and controls a heating temperature by adjusting amagnitude of the current.

In addition, as the forming system 100, a configuration shown in FIG. 4may be adopted. In the forming system 100 shown in FIG. 4 , the heatingunit 101 and the forming device 103 are provided as separate devices.Thus, the heating unit 101 can heat the metal pipe material 40 outsidethe forming die 102. In this case, the heating unit 101 heats the metalpipe material 40 to an A3 point or higher, that is, 800° C. or higher. Astate in which the heating unit 101 performs heating outside the formingdie 102 is a state in which heating is performed outside a space facingthe dies 12 and 11. In the example shown in FIG. 4 , the heating unit101 is provided at a position different from that of the forming device103. The metal pipe material 40 heated by the heating unit 101 is set inthe forming device 103 by a transport device such as a robot hand (notshown). Other configurations of the forming device 103 are the same asthose of the forming device 103 shown in FIG. 2 . The forming system 100that forms the flat plate-shaped metal material 50 as shown in FIG. 3may also have a configuration in which the heating unit 101 performsheating outside the forming die 102.

Alternatively, the heating unit 101 may perform two-step heating asshown in FIG. 18 . First, the heating unit 101 performs heating outsidethe forming die 102 (left figure of FIG. 18 ). At this time, the heatingunit 101 heats the metal pipe material 40 to 500° C. or higher and an A3point or lower, that is, 800° C. or lower. Next, the metal pipe material40 is transported together with the heating unit 101 into the formingdie 102 by the transport device (center figure of FIG. 18 ). Next, theheating unit 101 heats the metal pipe material 40 in the forming die 102(right figure of FIG. 18 ). In this case, the heating unit 101 heats themetal pipe material 40 to an A3 point or higher, that is, 800° C. orhigher. The first external heating of the forming die 102 may beperformed by a furnace or the like. As a result, it is possible tosuppress a decrease in degree of freedom of forming due to an increasein deformation resistance of the pipe, which is caused by a decrease inpipe temperature at the start of forming due to a decrease intemperature of the pipe being transported. In addition, when the metalpipe material 40 is heated by the forming die 102, since the heating isalready performed externally, it is possible to form the pipe whilesuppressing the deviation.

In addition, a configuration shown in FIG. 19 may be adopted. Theheating unit 101 shown in FIG. 19 performs two-step heating and performsnatural air cooling after first heating. First, the heating unit 101performs heating outside the forming die 102 (left figure of FIG. 19 ).At this time, the heating unit 101 heats the metal pipe material 40 to500° C. or higher and an A3 point or lower, that is, 800° C. or lower.Next, the metal pipe material 40 is removed from the heating unit 101,and natural air cooling is performed (center figure of FIG. 19 ). Next,the metal pipe material 40 is disposed in the heating unit 101 providedin the forming die 102, and the heating unit 101 heats the metal pipematerial 40 in the forming die 102 (right figure of FIG. 19 ). In thiscase, the heating unit 101 heats the metal pipe material 40 to an A3point or higher, that is, 800° C. or higher. The first external heatingof the forming die 102 may be performed by a furnace or the like.Accordingly, it is possible to suppress a deformation resistance of thepipe caused by a decrease in temperature of the pipe due to natural heatradiation. In addition, when the metal pipe material 40 is heated by theforming die 102, since the heating is already performed externally, itis possible to form the pipe while suppressing the deviation.

Returning to FIG. 1 , the plating deviation suppression mechanism 104 isa mechanism that suppresses the deviation of the plating in the metalmaterial due to energization heating. Here, the deviation of the platingof the metal material will be described. In the devices shown in FIGS. 2to 4 , the metal material can be quenched at the same time as theforming. However, in order to perform sufficient quenching, it isnecessary to heat the metal material to a temperature equal to or higherthan an Ac3 point for austenite transformation at the time ofenergization heating. Therefore, when the metal material is heated tosuch a high temperature, there is a possibility that oxide scales aregenerated on the surface of the metal material. In order to suppress thegeneration of such oxide scales, the surface of the metal material isplated with a plating material. Examples of the plating material includean AlSi plating material. Here, in a case where AlSi is used as theplating material, a melting point of aluminum is 652° C. which is lowerthan 900 to 1000° C. which is a temperature equal to or higher than anAc3 point which is a heating target temperature at the time ofquenching. Therefore, there is a possibility that the plating on thesurface of the metal material may be melted during energization heating.In such a melted plating, a strong attractive force acts in accordancewith the Fleming's left-hand rule due to a magnetic field generated by acurrent and the current, and a phenomenon in which the melted platingmoves (pinch effect), that is, a so-called deviation of the meltedplating occurs. When a plating thickness of the metal material becomesnon-uniform depending on locations, iron of a base material is exposed,which causes that the effect of suppressing the oxide scales is reduced.In a case of using the plated metal material, there is an issue that thedeviation of the melted plating occurs. For example, in a heatingprocess, an aluminum plating reacts with the iron of the base material,and an alloying reaction between the iron and aluminum proceeds to form,for example, an intermetallic compound (FeAl3) having a melting pointand a boiling point of 1000° C. or higher. In a case where a heatingrate is low, the alloying reaction proceeds before reaching the meltingpoint of 652° C. of the aluminum, and the melting of the aluminum isavoided. However, in a case where the heating rate is high and themelting point (652° C.) of the aluminum is reached before sufficientalloying proceeds, a part of the aluminum plating is melted, and theabove-described deviation occurs. Therefore, the plating deviationsuppression mechanism 104 suppresses the occurrence of such a deviationof the plating and secures the uniformity of the plating thickness ofthe metal material.

For example, FIG. 5A is a schematic cross-sectional view showing a statein which a plating 52 is uniformly formed on a surface of a basematerial 51 in the flat plate-shaped metal material 50. FIG. 5B is aschematic cross-sectional view showing a state in which the plating 52on the surface of the base material 51 has deviated to a predeterminedlocation in the flat plate-shaped metal material 50. FIG. 5C is aschematic cross-sectional view showing a state in which a plating 42 isuniformly formed on a surface of a base material 41 in the pipe-shapedmetal pipe material 40. FIG. 5D is a schematic cross-sectional viewshowing a state in which the plating 42 on the surface of the basematerial 41 has deviated to a predetermined location in the pipe-shapedmetal pipe material 40. When the plating deviation suppression mechanism104 is not provided in the forming system, the deviation of the platingoccurs as shown in FIGS. 5B and 5D. On the other hand, the platingdeviation suppression mechanism 104 can suppress the deviation of theplating to form a layer of the plating 52 having a uniform thickness, asshown in FIGS. 5A and 5C.

FIG. 6A shows a distribution of a magnetic field generated around themetal material 50 during energization heating in a case where theplate-shaped metal material 50 is energized and heated. In this case, asshown in FIG. 7A, when a current flows in one direction of the metalmaterial 50, a magnetic field is generated in the metal material 50, andthe distribution thereof is as shown in FIG. 7B. A direction and amagnitude of the magnetic field generated in the metal material 50 areschematically shown on the upper side of FIG. 7B, and a graph of themagnetic field of the metal material 50 is shown on the lower side ofFIG. 7B. In the metal material 50 during energization heating, a currentflows while generating such a magnetic field distribution. Therefore, aLorentz force according to the Fleming's left-hand rule acts. Thedirection and the magnitude of the magnetic field generated in the metalmaterial 50 are schematically shown on the upper side of FIG. 7C, and agraph of the Lorentz force of the metal material 50 is shown on thelower side of FIG. 7C. As shown in FIG. 7C, a direction of the Lorentzforce is a negative side in an X direction of the metal material 50 on apositive side in the X direction and is the positive side in the Xdirection of the metal material 50 on the negative side in the Xdirection (see FIG. 7C). Therefore, if the plating melts duringenergization heating, the melted plating deviates to the center in the Xdirection.

On the other hand, the plating deviation suppression mechanism 104 mayelectrically suppress the deviation of the plating. To electricallysuppress the deviation of the plating is to suppress the deviation ofthe plating by controlling a way to flow a current flowing through themetal material 50 by the heating unit 101. Specifically, the platingdeviation suppression mechanism 104 may suppress the current forenergization heating. In addition, such electrical suppression of thedeviation of the plating may be applied to any type of the formingsystem 100 of FIGS. 2 to 4 . In a case where the plating deviationsuppression mechanism 104 electrically suppresses the deviation of theplating, the plating deviation suppression mechanism 104 is composed ofthe heating unit 101 and the control unit 8 and 80 for controlling theheating unit 101. For example, FIG. 9 shows a graph CG1 of a currentwhen the plating deviation suppression mechanism 104 performs a currentcontrol for suppressing the deviation of the plating, and a graph TG1 ofa temperature transition when the current control is performed. Inaddition, a graph CG2 and a graph TG2 are graphs when the currentcontrol for suppressing the deviation of the plating is not performed.As shown in the graph CG1, the plating deviation suppression mechanism104 causes a current to flow in a state of being suppressed to a currentlower than that of the graph CG2 according to a comparative example. Inthis way, when the plating deviation suppression mechanism 104suppresses the current by performing the current control, the magneticfield shown in FIG. 7B becomes smaller, and as a result, the Lorentzforce from the center shown in FIG. 7C becomes smaller. Therefore, it ispossible to suppress the deviation of the plating. In addition, in thegraph CG1, a heating time is lengthened by an amount of suppression ofthe current. The plating deviation suppression mechanism 104 is notparticularly limited, but may suppress a current related to energizationheating to a range of 4 kA to 10 kA. When the current is larger than theabove range, the suppression effect is low, and when the current issmaller than the above range, energization heating takes too long. Inaddition, when the current is not suppressed, the current forenergization heating is in a range of 9 kA to 18 kA.

Further, in a case where the forming die 102, which is a magnetic body,exists near the metal material 50, a dielectric current as shown in FIG.8A is generated at the start of energization heating. Therefore, arepulsive force is generated in the metal material 50. On the otherhand, a dielectric current as shown in FIG. 8B is generated at the endof energization heating. Therefore, an attractive force is generated inthe metal material 50. Due to an influence of such a repulsive force oran attractive force, the deviation of the plating occurs. On the otherhand, the plating deviation suppression mechanism 104 may suppress achange in the current when the energization heating is stopped, as amethod of electrically suppressing the deviation of the plating. Forexample, when the energization heating is stopped, the plating deviationsuppression mechanism 104 does not abruptly stop the current (refer toan imaginary line) as shown at a location “A” in FIG. 9 , but graduallydecreases the current to reduce the current so as to draw a curve. Inthis way, by suppressing the change in the current when the energizationheating is stopped, it is possible to suppress the attractive forceshown in FIG. 8B and suppress the deviation of the plating. Although notparticularly limited, the plating deviation suppression mechanism 104may change the current in a range of, for example, about half of aninitial current value from the initial current value.

Next, the deviation of the plating of the metal pipe material 40 will bedescribed. FIG. 6B shows a magnetic field distribution when the metalpipe material 40 is energized and heated. Since the shape of the metalpipe material 40 is point-symmetrical, a surrounding magnetic field isalso symmetrically distributed. As a result, the magnetic field in adirection perpendicular to the surface of the material becomes zero(refer to FIG. 10B). Therefore, the attractive force in a tangentialdirection also becomes zero (refer to FIG. 10C) and the deviation of themelted plating is suppressed. On the other hand, as shown in FIG. 6C, ina case where a magnetic body such as the forming die 102 exists in thevicinity of the metal pipe material 40 at the time of energizationheating, the uniformity of the magnetic field distribution collapses. Asa result, the magnetic field in the direction perpendicular to thesurface of the material is generated. Therefore, an attractive force inthe tangential direction is generated in the metal pipe material 40(refer to FIGS. 12A to 12C), and a phenomenon occurs in which theplating deviates. In response to such a phenomenon of the deviation ofthe plating, the plating deviation suppression mechanism 104 maymechanically suppress the deviation of the plating. Mechanicallysuppressing the deviation of the plating means suppressing the platingby structural adjustment. In this case, the plating deviationsuppression mechanism 104 separates the metal pipe material 40 and themagnetic body (forming die 102) from each other by a predetermineddistance or more during energization heating. In this case, the platingdeviation suppression mechanism 104 is configured by the heating unit101 that positions the metal pipe material 40 during energizationheating. Alternatively, the plating deviation suppression mechanism 104is configured by the heating unit 101 that heats the metal materialoutside the forming die 102. In this case, the plating deviationsuppression mechanism 104 is configured by the heating unit 101 disposedexternally (refer to FIG. 4 ). The plating deviation suppressionmechanism 104 may be configured by a magnetic shield disposed around themetal material during energization heating. In addition, such a machineplating deviation suppression mechanism 104 may be applied to theforming system 100 for the flat plate-shaped metal material 50.

In a case where the plating deviation suppression mechanism 104separates the metal pipe material 40 and the magnetic body (forming die102) from each other by a predetermined distance or more, the distancemay be 20 mm or more. For example, as shown in FIG. 12B, when thedistance is 20 mm, the Lorentz force in the tangential direction becomeslarge, but when the distance is greater than 20 mm, the Lorentz forcecan be suppressed. The experiment shown in FIGS. 12A to 12C showsresults of analyzing the Lorentz force acting per unit area in fourcases where distances from the surface of the pipe to the die are 20 mm,50 mm, and 100 mm and the die is not present, assuming that an outerdiameter of the metal pipe material 40 is 60 mm, a plate thickness is 1mm, a pipe length is 1000 mm, and an energization current is 9000 A.

As shown in FIG. 11 , a magnetic shield 105 constituting the platingdeviation suppression mechanism 104 is configured to cover a peripheryof the metal pipe material 40 during energization heating. The magneticshield 105 is composed of two semi-circular members and covers the metalpipe material 40 by combining the two members during energizationheating. Further, at the time of forming, the magnetic shield 105 isretracted from the periphery of the metal pipe material 40.

Next, with reference to FIGS. 13 to 17 , an experiment for evaluatingthe effect of suppressing the deviation of the plating by the platingdeviation suppression mechanism 104 will be described. In thisexperiment, an AlSi-plated thick (150 g/m2) t 1.2 mm material of “Usibor(registered trademark)” was used as the metal pipe material 40. Inaddition, measurements were performed for a case where energizationheating is performed inside the forming die 102 and for a case whereenergization heating is performed outside the forming die 102. Theheating temperatures were 900° C., 1000° C., 1100° C., and 1200° C. inboth cases of internal heating and external heating. As a condition forinternal heating, the heating rate was controlled to be 15° C./sec and150° C./sec (first, a current value for a target heating rate wasconfirmed, and an experiment was performed with a fixed current value).As die positions in a case of internal heating, the upper die wasretracted to a position where there is no influence of the magneticfield, and lifting positions (lower die lifting positions) by theheating unit 101 were set to two positions of 45 mm and 70 mm for thelower die to perform measurements. When the lifting position is 45 mm, adistance between the metal pipe material 40 and the die is 15 mm, andwhen the lifting position is 70 mm, the distance is 40 mm.

FIG. 13 shows observation results of appearance under variousconditions. As shown in FIG. 13 , in a case where the lower die liftingposition is 45 mm and the heating rate is 150° C./sec, portions wherethe plating is thick are confirmed at positions on both sides adjacentto a bead position. That is, it is confirmed that the deviation of theplating occurs. Compared with the above result, it can be confirmed thatthe thickness of the plating is even under other conditions and thedeviation of the plating is suppressed. In particular, in a case ofexternal heating, it is possible to particularly reduce the deviation ofthe plating. Accordingly, it can be confirmed that the deviation of theplating can be suppressed by increasing the distance of the die orperforming heating externally.

FIGS. 14A to 16B are graphs showing a distribution of a height of thesurface of the metal pipe material 40 in a circumferential directionunder various conditions. From FIGS. 14A and 14B, it is possible toconfirm a correlation between the distance between the metal pipematerial 40 and the die and the deviation of the plating. In any ofFIGS. 14A and 14B, the larger the distance, the more the deviation ofthe plating can be suppressed. From this, it can be confirmed that asthe distance between the metal pipe material 40 and the surroundingmagnetic body (die or the like) increases, the deviation of the platingcan be reduced.

From FIGS. 15A, 15B, and 15C, it is possible to confirm a correlationbetween the heating temperature due to energization heating and thedeviation of the plating. In any of the graphs, it was not possible toconfirm a difference in the deviation of the plating due to the heatingtemperature. From this, it is considered that the deviation of theplating occurs during energization, and an influence of a final reachedtemperature is small.

From FIGS. 16A and 16B, it is possible to confirm a correlation betweenthe heating rate and the deviation of the plating. Since the deviationof the plating is smaller in FIG. 16B, it can be seen that there is atendency that the deviation of the plating can be suppressed when theheating rate is lower. It is considered that the small energizationcurrent reduces the Lorentz force, and the effect of progressingalloying in the heating process is contributed in the same manner as infurnace heating.

FIG. 17 is a bar graph showing the maximum height of the deviation ofthe plating under each condition. From the above graph, it is confirmedthat the effect of suppressing the deviation of the plating becomeslarge by increasing the distance between the metal pipe material 40 andthe die.

Next, operations and effects of the forming system 100 according to thepresent embodiment will be described.

The forming system 100 according to the present embodiment includes theheating unit 101 that causes the current to flow through the platedmetal material to heat the metal material, the forming die 102 thatforms the heated metal material, and the plating deviation suppressionmechanism 104 that suppresses the deviation of the plating in the metalmaterial due to energization heating.

In the forming system 100, the heating unit 101 causes the current toflow through the plated metal material to heat the metal material.Therefore, the plating may be melted by the heat of energizationheating. On the other hand, the forming system 100 includes a platingdeviation suppression mechanism 104 that suppresses the deviation of theplating in the metal material due to energization heating. Therefore, itis possible to suppress the deviation of the plating which is melted dueto energization heating. As described above, it is possible to suppressthe deviation of the plating of the metal material.

The plating deviation suppression mechanism 104 may electricallysuppress the deviation of the plating. In this case, the platingdeviation suppression mechanism 104 can easily suppress the deviation ofthe plating by electrical adjustment during energization heating.

The plating deviation suppression mechanism 104 may suppress a change inthe current when energization heating is stopped. In this case, in acase where a magnetic body exists around the metal material, it ispossible to suppress a magnitude of a force generated between the metalmaterial and the magnetic body due to a sudden change in the current.

The plating deviation suppression mechanism 104 may suppress the currentfor energization heating. In this case, in a case where the magneticbody exists around the metal material, it is possible to suppress themagnitude of the force generated between the metal material and themagnetic body during energization heating.

The plating deviation suppression mechanism 104 may mechanicallysuppress the deviation of the plating. In this case, a force generatedduring energization heating in relation to the magnetic body existingaround the metal material can be suppressed by structural consideration.

The plating deviation suppression mechanism 104 may separate the metalmaterial and the magnetic body from each other by a predetermineddistance or more during energization heating. In this case, it ispossible to suppress a force generated between the magnetic body and themetal material during energization heating.

The plating deviation suppression mechanism 104 may be configured by theheating unit 101 that heats the metal material outside the forming die.In this case, it is possible to suppress an influence of a forcegenerated between the forming die and the metal material duringenergization heating.

The plating deviation suppression mechanism 104 may be configured by themagnetic shield 105 disposed around the metal material duringenergization heating. In this case, it is possible to suppress thegeneration of the force between the forming die and the metal materialduring energization heating.

The present invention is not limited to the above-described embodiments.For example, the forming devices of FIGS. 2 to 4 are merely examples,and the forming device may have any configuration without departing fromthe concept of the present invention.

It should be understood that the invention is not limited to theabove-described embodiment, but may be modified into various forms onthe basis of the spirit of the invention. Additionally, themodifications are included in the scope of the invention.

What is claimed is:
 1. A forming system comprising: a heating unit thatcauses a current to flow through a plated metal material to heat themetal material; a forming die that forms the heated metal material; anda plating deviation suppression mechanism that suppresses a deviation ofa plating in the metal material due to energization heating.
 2. Theforming system according to claim 1, wherein the plating deviationsuppression mechanism electrically suppresses the deviation of theplating.
 3. The forming system according to claim 2, wherein the platingdeviation suppression mechanism suppresses a change in a current whenenergization heating is stopped.
 4. The forming system according toclaim 2, wherein the plating deviation suppression mechanism suppressesa current for energization heating.
 5. The forming system according toclaim 2, wherein the plating deviation suppression mechanism isconfigured by the heating unit and a control unit for controlling theheating unit, and the control unit is electrically connected to a powersupply of the heating unit and controls a heating timing by the heatingunit by transmitting a control signal to the power supply and controls aheating temperature by adjusting a magnitude of the current.
 6. Theforming system according to claim 1, wherein the plating deviationsuppression mechanism mechanically suppresses the deviation of theplating.
 7. The forming system according to claim 6, wherein the platingdeviation suppression mechanism separates the metal material and amagnetic body from each other by a predetermined distance or more duringenergization heating.
 8. The forming system according to claim 6,wherein the plating deviation suppression mechanism is configured by theheating unit that heats the metal material outside the forming die. 9.The forming system according to claim 6, wherein the plating deviationsuppression mechanism is configured by a magnetic shield disposed aroundthe metal material during energization heating.
 10. The forming systemaccording to claim 9, wherein the magnetic shield is composed of twosemi-circular members and covers the metal material by combining the twomembers during energization heating.
 11. The forming system according toclaim 10, wherein the magnetic shield is retracted from a periphery ofthe metal material at the time of forming.